Simplitron magnetron



Sept 15, 1953 c. v. LlTToN 2,652,516

SIMPLITRON MAGNETRON Filed Oct. 21, 1949 ATTORNEY Patented Sept. 15, 1953 SIMPLITRQN MAGNETEON Charles. V. Litton, RedwoodA City, Calif.

Application OctoberV Z1, 1949, Serial No. 122,634

6 Claims.

This invention relates to. magnetrons, and more especially to magnetrons for operation at very high frequencies.

A principal object is to provide a magnetron assembly which is capable of efficient operation at frequencies of the order of 8 to 50 centimeters wavelength.

I have disclosed in my prior application Serial No` 694,259, led August 31, 1946, now Patent No. 2,551,614, granted May 8, 1951, a novel and simplified construction of magnetrons employing a single vane which cooperates with a magnetron anode-cavity to produce very high frequency oscillations. The present invention is in the nature of an improvement on the electrode arrangement and mounting of that type of magnetron device.

A feature of the invention relates to an improved electrode mount for very high frequency magnetrons, whereby the utmost dimensional accuracy can be achieved with the desired operational stabilty of the magnetron `and without correspondingly increasing the cost of manufacture and assembly.

Another feature relates to a novel construction of lament end cap shielding arrangement for magnetrons of the single magnetron cavity type.

A further feature relates to a simplified magnetron tube for use at very high frequencies, wherein the parts are designed to facilitate accurate assembly and alignment by conventional assembling techniques.

The above-mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent, and the invention will be best understood, by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

' Fig. 1 is an isometric perspective view, partly sectional, illustrating the electrode arrangement.

Fig. 2 is a longitudinal sectional view of Fig. 1.

Fig. 3 is a sectional View of Fig. 2 taken along the line 3--3 thereof.

Fig. 4 is a sectional view of Fig. 2 taken along the line 4--4 thereof.

Fig. 5 is a sectional view of Fig. 1 taken in a plane at right angles to the sectional plane on which Fig. 2 is taken.

Fig. 6 is a schematic wiring diagram of the circuits for energizing the magnetron of Figs. 1 to 5.

Referring to Figs. 1 to 5, the magnetron comprises a glass stem or header I of any Well-known form, and it may comprise a reentrant neck 2 terminating in a cruciform press 3. A suitable exhaust tubulation 4 is provided for evacuating thev completed tube. Sealed in a vacuum-tight manner through the press 3 are two lead-in wires or rods 5, Ii, which conduct the heating -current to the filamentary cathode. l. This cathode may be in the form of a convoluted or helical wire carrying the usual coating of electron-emissive material, such as is well known in electron discharge devices generally.

Also sealed into the press, preferably in a plane perpendicular to the plane of rods 5, 5, are two metal rods 8, 9, which are tightly tted and suitably anchored into one end of a metal anode block I0. As shown more clearly in Fig. 4, the block lll is circular in cross-section except for the recesses II, I2, on opposite sides. These recesses are sufficiently large in cross-section to allow the lament rods 5, E, to pass freely therethrough without any danger of short-circuiting to the anode.

The end of block ID remote from the press is formed with a central rectangular projection i3 which has its forward end undercut to form a cylindrical recess or cavity 14. This cavity Ill has a window I5, and preferably the edges I6, I?, thereof are chamfered.

Sealed or otherwise fastened to each of the rods 5, 6 are metal buttons or caps I8, IS, each cap having a central recess into which the respective opposite ends of the coiled lamentary cathode 'l are fitted. The ends of this filamentary cathode are prefer-ably welded to the caps Iii and I9. These caps have a diameter which is greater than the diameter of the circular cavity Ill, and they are preferably provided with reduced. shoulders 2B which are located in close proximity to, but spaced from, the ends of cavity I4. Thus the ends of the said cavity are substantially entirely protected against the emergence of electrons from the opposite ends thereof. The foregoing elements form a structural unit.

In order to complete the enclosing envelope, there is provided another structural unit, consisting of the tubular glass member 2i which is sealed at 22 to the stem I. The opposite end of member 2| has sealed in a Vacuum-tight manner thereto, a tubular metal member 23 with the opposite ends provided with feathered edges 24, 25. The edge 24 is sealed in the well-known manner into the body of the glass member ZI. The end 25 has sealed thereto a glass button 26 which also has sealed centrally therethrough a metal rod 2l preferably, although not necessarily, of tungsten. The member 23 has a shoulder portion 28 which is adapted to seat against a corresponding shoulder 29 on the anode block IQ. The member 23 can be made of copper, or other similar metal or alloy which can be sealed in a vacuum-tight manner to the glass members 2l and 26. In order to facilitate assembly of the parts, the reduced portion 3U of member 23 can be provided with a longtiudinal inwardly-formed bead 3l which is arranged to register with a corresponding longitudinal recess or groove 32 in the wall of anode block i0. Thus by reason of the cooperating shoulders 28, 29, and the cooperating rib 3| and groove 32, the parts can be readily assembled with the desired degree of accuracy.

As shown in Figs. 1, 2 and 5, the end of rod 21 adjacent cavity I4 is provided with a taper 33. Preferably the parts are so dimensionally related that the distance between the extreme end 34 of rod 21 and the opposite wall of cavity M is approximately equal to the cavity diameter, and the spacing between the edge 3S and the cavity edges le and l1 of the cavity window are correlated with the frequency for which the magnetron is designed to be used. In the Wellknown manner, a suitable magnet having the respective north and south pole pieces 35, 36 is mounted with respect to the cathode 1, so as to cause the emitted electrons to travel in the proper trajectories around the longitudinal axis or the cathode, and so that these trajectories intercept the cavity edges l5, l1, and the edge in the proper phase relation to generate oscillations. It will be understood, of course, that a suitable direct current potential is applied to the anode id and to the rod 21, which potential relatively high compared to the cathode potential. Ii desired, the magnet is mounted in an adjustable cradle so that its orientation around the member 3&3 can be adjusted to achieve the proper electron trajectories. Arranged to be telescoped over the end of member it is the outer tubular conductor 31 of a coaxial wave transmission line whose center conductor is also arranged to be connected to the rod 21. An adjustable plunger 38 which operates as a combination tuner and output transformer is mounted within the conductor 31. The member 3B and the portion 3i of the coaxial line form, together with the end of member 30, a cavity resonator which can be tuned by adjustment of the plunger The plunger 3B provides a short between conductors 21 and 31, the plunger 38 being shaped to provide an abrupt discontinuity on the tube side and a tapered transformer on the load side. The abrupt end of the plunger is provided with a slideable Contact 38a in engagement with conductor 3? and a grounding coil 33h in engagement with conductor 21. This exponential transformer is broad band and provides uniform loading over` the useful band.

It will be understood, of course, that any other well-known manner of tuning the cavity can be provided. For example, the insulator member 2E carrying the rod 21 can be sealed to the end of member 33 by a metal bellows or sylphon whose erective length can be adjusted. Likewise, if desired, the rod 21 can be sealed to the member 25 by a separate metal bellows or sylphon so as to adjust the spacing between the edge and the magnetron cavity IG.

ig. 6 shows, in schematic form, the various elements of the magnetron, together with the appropriate potential supplies therefor. Thus the filamentary cathode 6 is provided with a suitable heating supply current source 39, and a suitably high direct current potential source lill has its negative end connected to the cathode 5 and its positive end connected through a suitable high frequency choke coil 4| to the anode I0 and to the electrode 21. If desired, the anode lil and electrode 21 may be connected to separate and adjustable direct current supplies so as to vary the relative direct current potentials for the required frequency of oscillation from the magnetron. Y

While I have described above the principles oi my invention in connection with specic apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention.

What is claimed is:

1. A magnetron, comprising a tubular metal member having means closing oi each end in a vacuum-tight manner, a metal anode block telescopically iitted into said tubular metal member, said block having means .eiining a single cavity therein with one wall of the cavity having a magnetron gap, another anode having edge in spaced registry with said gap, and an electronemitting cathode centrally mounted within said cavity.

2. A magnetron, comprising an evacuated envelope constituted in part of a tubular metal member, a metal anode block telescoped into said tubular member, said block having one end provided with a magnetron cavity therein having a single magnetron gap which in plan crosssection is substantially the shape of a circle, an electron-emitting cathode centrally mounted within saidV cavity, magnetic means disposed at opposite ends of said cavity for causing the electrons to precess around said cavity and past said gap, and another anode having a substantially linear edge in registry with said gap and symmetrically spaced from the edges of the gap and said edge being located substantially on said circle.

3. A magnetron, comprising an evacuated envelope constituted in part of a tubular metal member, a metal block telescoped into said tubular member, said block having one end provided with a magnetron cavity therein having a single magnetron gap, an electron emitting cathode centrally mounted within said cavity, magnetic means disposed at opposite ends oi" said cavity to cause the electrons to precess around said cavity and past said gap, and another electrode having a substantially linear edge in registry with said gap and symmetrically spaced from the edges of said gap, said block being substantially circular in cross-section and provided at said one end with an integral and substantially rectangular projection in which said magnetron. cavity is formed.

4. A magnetron, comprising an evacuated envelope having a header at one end, a plurality of lead-in conductors sealed in a vacuum-tight manner .through said header, a tubular metal member forming part of the wall of said envelope, an anode block supported from one of said lead-in members and telescoped within said tubular metal member, said block having means defining a transverse magnetron cavity, said Cavity having a single gap, an electron emitting cathode located Within said cavity, means includ- -ing a pair of said lead-in conductors supporting said cathode at its opposite ends, and another anode having an edge in registry with said cavity and symmetrically spaced from the edges of said gap.

5. A magnetron, comprising an evacuated envelope consisting of a glass header, a tubular metal member sealed to said glass header, said tubular metal member having a peripheral shoulder, a lead-in conductor sealed through said header, an anode block attached to the inner end of said conductor, said anode block having a shoulder in abutment with the shoulder on said tubular metal member, a cooperating rib and recess on said tubular metal member and said block for preserving a predetermined orientation of the block with respect to the tubular metal member during the assembly thereof, said tubular metal member overhanging the end of said block, an insulator member sealing-off the open end of said tubular metal member, means in said block dening a substantially cylindrical magnetron cavity with a single magnetron gap, an electron-emitting cathode symmetrically located within said magnetron cavity, a plurality of lead-in members sealed through said header and passing along said block supporting said cathode at opposite ends, and another electrode passing through said insulator sealing member and having an edge in registry with said magnetron gap to bisect said gap.

6. A magnetron tube having an evacuated envelope comprised of a glass stem with a plurality of lead-in conductors sealed therethrough, a tubular metal member forming part of said envelope and sealed at one end to said stem, an insulator button sealing the opposite end of said tubular member, said tubular member having a peripheral shoulder and a longitudinally extending rib, a metal anode block tted within said tubular member and having a peripheral shoulder and a longitudinally extending groove for respective registry with the shoulder and rib 0n said tubular member, said block having a pair of oppositely disposed longitudinally extending grooves through which freely pass a pair of said lead-in conductors, said block having a magnetron cavity with a single magnetron gap 1ocated adjacent the ends of said pair of conductors, electron shielding caps attached to the said ends of said pair of conductors, an electron-emitting cathode connected at its opposite ends to said caps and passing through said magnetron cavity, and another electrode sealed through said insulator button and extending with its edge adjacent said magnetron gap.

CHARLES V. LITTON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,115,521 Fritz et a1 Apr. 26, 1938 2,163,157 Samuel June 20, 1939 2,171,980 Hansell Sept. 5, 1939 2,196,392 Hansell Apr. 9, 1940 2,428,193 Blewett Sept. 30, 1947 2,460,119 Blewett et al Jan. 25, 1949 2,462,698 Wilbur Feb. 22, 1949 2,466,765 Hartman Apr. 12, 1949 2,599,270 Megaw June 3, 1952 

